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Cancer Treatment Centers of America

Colorectal cancer symptoms

Colorectal cancer symptoms may be minimal or non-existent during the early stages of the disease. The signs and symptoms of colorectal cancer may not arise until the disease has progressed into stage II or beyond. Regular screening tests for colon and rectal cancer, especially with a colonoscopy, is recommended as part of a health plan for anyone over 50 years old or anyone under 50 who are at high risk or have a family history of the disease or other cancers. Talk with your doctor about when you should start regular colorectal cancer screening.

Several tests may be used to diagnose colorectal cancer. These tests may include a colonoscopy, or other endoscopic procedures, stool tests, or other lab tests, or an MRI, CT scan or PET/CT scan. In many cases, a biopsy may be required. These imaging and laboratory tests may also be used to track the size of tumors and monitor response to treatment.

Learn more about diagnostic evaluations for colorectal cancer.

colorectal cancer symptoms

Colon cancer symptoms

The colon, or large intestine, absorbs water and nutrients and helps process food into waste. Colon cancer may affect the large intestine's ability to perform some of these functions, causing changes in bowel habits or unexplained weight loss.

One way colon cancer may develop is from polyps, small growths that form along the inside lining of the colon. Polyps are often benign or pre-cancerous in the beginning, but if allowed to grow, they may develop into cancer and may spread into the colon wall, causing noticeable symptoms. Polyps and other early signs of colon cancer may be detected and removed during regular screening with a colonoscopy. Consult your doctor on when you should start a screening schedule.

During stage I of colon cancer, no obvious signs or symptoms may have developed. As symptoms develop, they may vary depending on the tumor's size and location in the large intestine. Early symptoms may affect only the colon and result in changes in bowel habits. As the cancer grows, it may spread, producing systemic symptoms that affect your whole body, such as fatigue and weight loss.

Some changes in bowels habits that may be considered colon cancer signs include:

  • Change in frequency of bowel movements
  • Constipation
  • Change in consistency of stool (loose or watery stools)
  • Blood in stools (either as bright red spots or dark tar-like stools)
  • Rectal bleeding
  • Abdominal pain, bloating or cramps
  • A persistent feeling that you cannot completely empty your bowels


Last Revised: 06/18/2018

Understanding cancer symptoms

These symptoms may be attributed to a number of conditions other than cancer. If you notice any cancer signs or symptoms, it's important to visit your doctor for an accurate diagnosis.

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